Thermosensitive switch mechanism



May 26, 1959 J. s. MEARS EIAL 88,

THERMOSENSITIVE SWITCH MECHANISM Filed Oct. 8. 1957 IIIVEN'IDRS cfohn S. Mec rs Dominic f. Delorenz 1's W Max AH'ys.

United States Patent THERMOSENSITIVE SWITCH MECHANISM John S. Mears, Oswego, and Dominic F. Delorenzis and Stanley E. Watson, Portland, 0reg., assignors to Mears Electric Controls, Inc., Portland, Oreg., a corporation of Oregon Application October 8, 1957, Serial No. 688,862 Claims. (Cl. 200-138) This invention relates to thermosensitive control mechanism, and more particularly to thermosensitive electric switch mechanism adapted to control electric current transmitted to an electric work element.

Thermosensitive controls are commonly used to control the operation of means for heating rooms, air conditioner units, electric blankets, heating pads, stove elements, and the like, to regulate their operation in response to temperature change. Generally, it is an objeet of this invention to provide improved thermosensitive control mechanism which may be constructed with the requisite sensitivity to temperature change, and which is also a highly compact unit capable of being mounted in a relatively confined space.

Another object is to provide thermosensitive control mechanism of relatively simple construction which may be produced economically without sacrifice of sturdiness or sensitivity.

The thermosensitive control mechanism of this invention features a casing having a base portion to which is secured a conventional switch used for controlling an electrical circuit. This switch may take the form of a microswitch, extensively employed for making and breaking the electrical circuit to room heaters, refrigerators, and other electrically controlled equipment. The base portion mounting the microswitch is provided with a pair of extensions which lie in planes disposed at right angles relative to the base portion. These extensions define an enclosure for the microswitch and shield the switch from damage.

Aflixed to an end portion of one of the extensions is a thermosensitive strip, such as a bimetallic strip, which is subject to deformation in response to ambient changes in temperature. The thermosensitive strip, together with the base portion and extensions, surround the microswitch. One end of the thermosensitive strip is disposed adjacent the actuating member for the microswitch.

The extension mounting the thermosensitive strip is flexible and resilient. The flexibility of the extension provides a means for adjusting the position of the thermosensitive strip relative to the actuating member for the switch. This enables adjustment in the temperature response of the switch. A full cantilever mounting is used for the thermosensitive strip, the strip deforming in response to temperature change throughout its entire length.

The use of a full cantilever mounting for the thermosensitive strip results in economy of manufacture, and a compact design without sacrifice of sensitivity or ruggedness of construction. Adjustment of the temperature response of the switch is readily made by the simple expedient of adjusting the position of the extension mounting the strip.

The invention features a variable length screw mechanism for adjusting the position of the extension mounting the thermosensitive strip. The projection of the screw mechanism outside the casing for the control mechanism remains the same at all times. The overall space requirements of the unit, therefore, remains substantially the same regardless of the adjusted position of the parts in the mechanism.

Other objects, novel features and advantages of the invention will become more fully apparent as the following description is read in conjunction with the accompanying drawings wherein:

Fig. 1 is a plan view of thermosensitive control mechanism constructed according to an embodiment of this invention;

Fig. 2 is a side view of the control mechanism illustrated in Fig. 1;

Fig. 3 is a section view along the line 3-3 in Fig. 1, showing the relative position of the thermosensitive strip with respect to a microswitch mounted within the unit; and

Fig. 4 is a section view along the line 4-4 in Fig. 1, showing the mounting for the variable length screw mechanism employed in the control mechanism.

Referring now to the drawings for a more detailed description of an embodiment of this invention, 10 indicates a casing for the control mechanism which includes a flat base portion 11 or mounting base extending along one side of the control mechanism, and a pair of arms or extensions 12 and 13 integral with base 11 but arranged so that the arms lie in planes disposed at substantially right angles relative to base 11. This is accomplished by turning over one edge of base 11 to form a flange 16 or support flange disposed at right angles relative to the base. Extensions 12 and 13 are integral with flange 16 and are formed by continuing the flange at each of its ends.

Mounting portion 10 may be comprised of steel or similar material of a slightly resilient and flexible nature. The outer end of arm 12, that is the portion of arm 12 carried on the left of the casing in Fig. 1, is situated a considerable distance from its connection with flange 16 and the base. This permits the outer end of arm 12 to flex toward and away from support flange 16. Flange 16 is directly joined throughout the length of the flange at its base to base 11, and thus provides a substantially solid support.

Secured to base 11 of the casing is an electrical switch indicated generally at 21. The details of switch 21 are not illustrated because they are generally known to persons skilled in the art, and a commercially available switch may be used.

In general terms, the switch includes terminals connected to wires 22 and 23, and suitable mechanism within the body of the switch to make and break the connection between these terminals. A switch actuating member, such as button 26 protruding outwardly from one side of the switch body, moves in and out relative to the body of the switch to actuate the mechanism making and breaking the connection. Wires 22 and 23 lead to the electrical element controlled by the thermosensitive control mechanism. The wires enter through a rubber grommet 27 carried in an accommodating aperture formed in extension 13. Switch 21 is aflixed to base 11 as by screws 28 and 29.

Aiiixed to the outer end of arm 12 is a U-shaped ther mosensitive strip 31. The strip is secured near the lower edge of arm 12 by screws 32. Referring to Figs. 1 and 3, the strip extends first outwardly from base 11 and thence over the side of switch 21 which is disposed away from base 11 so as to cover the exposed side of the switch. The strip then bends downwardly as viewed in Fig. 3 so that its free end lies adjacent to button 26. Thermosensitive strip 31, which may be a bimetallic strip, is sensitive to temperature changes, deforming with temperature changes so that the free end of the strip moves in and out over button 26, thereby to actuate the button and the switch mechanism controlled thereby.

"aseasse It will be noted that strip 31 is fastened to extension 12 at one of its ends so that a full cantilever mounting is used for the strip. The strip is readily sensitive to temperature change, the entire length of the strip between its connection with arm 12' and button .26 responding to temperature change.

Means are interposed between the free or outer end of arm 12 and support flange 16 for adjustably fixing the spacing between the two. In the embodiment illustrated, this mechanism takes the form of a variable length screw mechanism, indicated generally at 36. Referring to Figs. 1 and 4, the screw mechanism includes a nut portion 37 aflixed to the outer end of arm 12 as by screw 38. Internal threads in the end of nutportion 37 receive the end of a screw member 39. The other end of. screw member 39 extends outwardly through support flange 16. This other end may be provided with a flat edge 41 for attaching nonrotatably a conventional handle used for adjusting the switch. Snap rings 42 and 43 rotatably hold the screw member against shifting axially relative to flange l6.

It will be noted that adjustment of the screw mechanism varies the dimension of the mechanism between arm or extension 12 and support flange 16. In this way the protrusion of the screw mechanism to either side of the casing is never changed, as would be the case if a continuous solid screw were used and the screw were advanced through the unit or retracted from it during adjustment. The screw mechanism, together with the novel casing construction employed, reduce substantially the overall space requirements of the unit.

Screw member 39 is restrainedfrom rotary movement in one direction by pin 46 extending outwardly from the body or shank of the screw member and operable to engage a flange ,or shoulder 47 formed by turning up a portion of base 11..

Arms 12 and 13 together with flange 16 define an enclosure over one side of the base which surrounds the switch. Flange 16 and arm 12 bound three sides of the switch, extension 13 defining the other side of the enclosure.

The construction of this invention may be economically produced and is characterized by a high degree of temperature sensitivity relative to its size. Adjustment of the spacing of the outer end of arm 12 with respect to flange 16 adjusts the temperature response of the control mechanism. 7

While a single embodiment of this invention has been described, it is not intended to be limited to the specific embodiment illustrated, but rather to cover all modifications and variations which would be apparent to one skilled in the art and that come within the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. Thermosensitive control mechanism comprising a mounting base, a flexible arm integral with said mounting base having an end portion movable relative to said mounting base, a support flange integral with said mounting base spaced from and disposed opposite said end portion of said arm, a switch having an actuating member, said switch being aflixed to said mounting base intermediate said arm and flange with said actuating member projecting toward said flange, a thermosensitive strip rigidly aflixed at one end to said end portion of said arm and with its other end adjacent said actuating member with portions intermediate the ends of said strip in covering relation over said switch, and means interposed between said arm and support flange for adjustably fixing the spacing between the two and thereby the position of said other end of said strip relative to said actuating member.

2. Thermosensitive control mechanism comprising a mounting base, a flexible arm integral with said mount- '4 ing base having an end portion movable relative to said mounting base, a support flange integral with said mounting base disposed opposite said end portion of said arm, a switch having an actuating member, said switch being aflixed to said mounting base intermediate said arm and flange with said actuating member projecting toward said flange, a thermosensitive strip rigidly aflixed at one end to said end portion of said arm and with its other end adjacent said actuating member with portions intermediate the ends of said strip in covering relation over said switch, and adjustable variable length screw mechanism mounted at one end in said arm and at its other end in said flange, adjustment of said screw mechanism varying the dimension ofthe mechanism between said arm and flange, said screw means adjustably fixing the spacing between said arm and flange thereby to adjust the position of said other end of said strip relative to said actuating member. 5'

3. Electrical thermostat mechanism comprising a. casing having a base portion and integral with said base portion a flange turned at substantially right angles relative to said base portion, said flange having an extension integral therewith, and said extension having aportion spaced oppositely to said flange, said oppositely disposed portion being free of said flange and base portion and movable relative thereto, said extension describing with said flange a confined area over one side of said base portion bounded on at least three sides, an electric switch having a switch actuating member aflixed to said base"portion within said confined area, said actuating member projecting toward said flange, a thermosensitive strip rigidly aflixed at oneend to said oppositely disposed portion of said extension with the other end thereof adjacent said actuating member, and means interposed between said oppositely disposed portion of said extention and said flange for adjustably fixing the spacing between the two and thereby the position of said other end of said strip relative to said actuating member.

4. Thermosensitive control mechanism comprising a casing having a base portion and integral with said base portion a flange turned at substantially right angles relative to said base portion, said flange having an extension integral therewith describing with said flange a confined area over one side of said base portion bounded on at least three sides, a switch having a switch actuating member afiixed to said base portion within said confined area, a thermosensitive strip aflixed to said extension with an end thereof adjacent said actuating member, and adjustable variable length screw mechanism mounted at one end in said extension and at its other end in said flange, adjustment of said screw mechanism varying the dimension of the mechanism between said extension and flange, said screw means adjustably fixing the spacing between said extension and flange thereby to adjust the position of said end of said strip relative to said actuating member.

5. Thermosensitive control mechanism comprising a casing having a base portion and integral with said base portion a flange turned at substantially right angles relative to said base portion, said flange having an extension at each end integral therewith describing with said flange an enclosed area over one side of said base por tion, one of said extensions together with said flange bounding three sides of said enclosure, a switch having tion, and adjustable variable length screw mechanism s mounted at one end in said end portion of said one exto adjust the position of said other end of said strip tension and at its other end in said flange, adjustment relative to said actuating member. of said screw mechanism varying the dimension of the References Cited in the file of this Patent mechanism between said one extension and flange, said screw means adjustably fixing the spacing between said 5 UNITED STATES PATENTS end portion of said one extension and said flange thereby 2,613,298 Armstrong 1952 2,792,473 Hawke May 14, 1957 

